But his Australian naturalization file from 1910, held in the National Archives of Australia's collection, provides a tantalising glimpse into his life on the run, as police from various countries wrote to warn each other of his activities.

One letter warned: 'He has no money, he lives on his wits... there is strong reason to believe he is a Bolshevik emissary'. A letter from New Scotland Yard in 1929 said he was a dental practitioner who married his surgery attendant but 'the wife alleged her husband frequently associated with other women'. The police in Ceylon warned that he 'tried to get a Russian woman out from England... Permission was refused as his intentions appeared to be immoral.

He moved from Britain to Australia (where he was naturalised in 1910) to Britain again, then to Ceylon (Sri Lanka) and South Africa, from where he was deported to Australia (who unsuccessfully tried to find a reason for not allowing him back in).

At various times, he gave his occupation as a stationer and photographer, dentist and former director of medical research at Kharnon University, Russia. He eventually found fame as a naturopath, extolling the virtues of soybeans and vegetable juice therapy. His views are still quoted by certain health practitioners.

He came to the notice of Australian Intelligence in September 1939 after police received an anonymous letter accusing Koonin of being a Russian spy and wireless expert. It said he was 'very poor until two months ago. Just keep him under observation'.

National Archives Director of Digital and Online Access Zoe D'Arcy came into the studio to tell us more about the mysterious Paul Koonin on Treasure Trove.